The more we hear, the more likely it is that the final season of Game of Thrones could be held back until 2019.

Work has begun on season eight, but as Iain Glen – who plays Ser Jorah in the HBO fantasy epic – revealed at Comic-Con Stockholm last month, the initial read-through with the actors has been slated for October 9.

The actor then shared his thoughts on the reasons behind the much-speculated longer shoot.

"We're all starting to occupy the same territory," he said. "We're all starting to be in the same storylines and so they can't [have two filming units] anymore. I think this last season will take much longer to shoot because they can only use one unit, because we're all in the same sort of scenes."

HBO previously commented on the complications of making the final season, as production on the last six episodes could finish as late as August 2018.

"Our production people are trying to figure out a timeline for the shoot and how much time the special effects take," programming boss Casey Bloys said.

"The shooting is complicated enough – on different continents, with all the technical aspects – and the special effects are a whole other production period that we're trying to figure out. That is a big factor in all of this."

Speaking of the final season, it has been reported that it will cost HBO $15 million per episode to make.